Sitel is a telemarketing and outsourcing business headquartered in Nashville, Tennessee. It maintains 108 sites in 21 countries.

Prior to its acquisition by ClientLogic, described below, it had 70 call centers in 25 countries and over 30,000 employees. It maintains offices in its previous headquarters location of Omaha, Nebraska but its headquarters was moved to ClientLogic's headquarters in Nashville.

The original SITEL (Systems International TELemarketing) was founded in 1985 by James F. Lynch, as a result of his purchase of HQ800, an answering service company owned by United Technologies, for just $165,000. After the signing of its first major client in 1988, Allstate Insurance, SITEL's client list rapidly grew. Today the company serves many Fortune 500 companies, and some of the world's largest, most well-known brands.

In June 1985, SITEL became the first publicly traded, independent teleservices company and was listed on the NASDAQ through an initial public offering (IPO). Six months later, they moved from NASDAQ to the NYSE as 'SWW'.